Field of the Invention
The present invention relates to an apparatus for analyzing an image formed by an image forming apparatus to determine an abnormality, and also to an abnormality determination method.
Description of the Related Art
Printers, copying machines, and facsimiles are known as image forming apparatuses for forming an image on a recording material such as paper. For example, in a case of an electrophotographic image forming apparatus, a service engineer performs maintenance services to maintain the image quality of an image formed on paper. Photosensitive members and an intermediate transfer belt are examples of parts which are consumed accompanying the operations of an image forming apparatus. Such consumables are replaced with new ones by the service engineer as maintenance services. Factors for causing consumption of component parts generally include: friction and wear accompanying image forming operations, mixing of paper powder into a toner image, increased adhesive force due to excessive stirring of toner and detachment of external additives, and contamination and degradation of cleaning and charging members caused by toner and paper powder. These factors may degrade the image quality of an image formed on paper. Examples of abnormal images with degraded image quality include:
(1) An abnormal image having lateral stripes perpendicular to the rotational direction of the photosensitive member and intermediate transfer belt (also referred to as an image of laterally uneven density)
(2) An abnormal image in form of spots (also referred to as a black-dot image)
(3) An abnormal image having longitudinal stripes along the rotational direction of the photosensitive member or an intermediate transfer belt (also referred to as an image of longitudinally uneven density)
When any such abnormal images is formed on a recording material, a user notices the abnormal image and replaces the component parts such as the photosensitive drum and the intermediate transfer belt. If the user addresses a problem only after he visually notices an abnormal image, time will be consumed from occurrence of the abnormality until completion of addressing the problem. In addition, the recording material on which the abnormal image is formed will go to waste. Since image formation needs to be carried out again, toner will be wastefully consumed.
Japanese Patent Application Laid-Open No. 2004-discusses an apparatus which forms and outputs a sample image different from a usual image on a recording material, reads the sample image formed on the recording material by using a reading scanner (image input unit), and, based on the read image, finds an early sign of the abnormal image at the time of image formation. This enables finding the sign of the abnormality before the abnormality occurs at the time of normal image formation, and a necessary measure can be taken at an early stage. Japanese Patent Application Laid-Open No. 2014-16437 discusses a technique for detecting feature quantities of an abnormal image from the image read by the reading scanner (image input unit) and determining the time-sequential characteristics regarding the feature quantities of the abnormal image at a plurality of timings. Thus, a defective portion causing the abnormal image can be determined and information about failure is notified.
Such conventional techniques enable predicting the occurrence of an abnormality in advance or identifying a defective portion. Thus, the downtime of the image forming apparatus can be reduced by preparing and using replacement parts.
Further improvement in the accuracy is now demanded with respect to the system for detecting the sign of the abnormality discussed in Japanese Patent Application Laid-Open No. 2004-133081 and the system for determining a defective portion discussed in Japanese Patent Application Laid-Open No. 2014-16437. Since there are a number of types of abnormal images, it is necessary to choose feature quantities suitable for the type of each abnormal image. Although feature quantities can be time-sequentially determined as discussed in Japanese Patent Application Laid-Open No. 2014-16437 to a certain extent, the accuracy and reliability are limited in this method. If the type of image abnormality is incorrectly determined, for example, the method may prompt the user to replace the parts which are still fully usable. On the other hand, the method may also prompt the user to replace the parts in a delayed fashion. If the replacement of the parts is delayed, the apparatus may become unusable.